Refactor Channel endpoints and data models: replace jingle functionality with bumper templates, update related commands and handlers, and enhance API routes for managing bumper templates. Remove obsolete jingle-related code and adjust channel data structures to support new bumper template features.

backend/src/TeleWave.Application/Broadcast/Bumpers/ClearBumperTemplateAudioCommand.cs

@@ -0,0 +1,8 @@
+using LiteCqrs;
+using TeleWave.Application.Common.Models;
+
+namespace TeleWave.Application.Broadcast.Bumpers;
+
+/// <summary>Удалить загруженный звук блока (вернуться к синтезированному джинглу).</summary>
+public sealed record ClearBumperTemplateAudioCommand(Guid ChannelId, Guid TemplateId)
+    : ICommand<Result>;